Chap. I. SERVICEABLE ASSOCIATED HABITS. 49 



of the mind, are partially repressed by the will, the 

 strictly involuntary muscles, as well as those which are 

 least under the separate control of the will, are liable 

 still to act; and their action is often highly expressive. 

 Conversely, when the will is temporarily or permanently 

 weakened, the voluntary muscles fail before the involun- 

 tary. It is a fact familiar to pathologists, as Sir C. Bell 

 remarks, 20 " that when debility arises from affection of 

 the brain, the influence is greatest on those muscles which 

 are, in their natural condition, most under the command 

 of the will." "We shall, also, in our future chapters, con- 

 sider another proposition included in our first Principle; 

 namely, that the checking of one habitual movement 

 sometimes requires other slight movements; these latter 

 serving as a means of expression. 



20 * 



Philosophical Translations,' 1823, p. 182. 



